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Purpose: To evaluate the influence of different implant numbers and connection types on the biomechanical behavior of mandibular full-arch implant-supported rehabilitation. Materials and Methods: Computed tomography-based finite element models comprising a totally edentulous mandible and 3.8 × 13-mmdiameter implants, abutments, abutment screws, bar retaining screw, and bar were constructed. Different implant numbers (three, four, and five implants) and loading conditions (symmetrical/balanced, unilateral, and posterior with diverse loading magnitudes) were simulated for both external hex and Morse-taper connections. The peak equivalent strain (EQV strain) in the bone and the peak of von Mises stress (EQV stress) in the abutment screw and bar retaining screw were evaluated. Results: Lower strain values were observed for a symmetrical loading distribution. Considering the same loading conditions, significantly higher bone strain levels were observed for external hex, compared with the Morse-taper connection. The number of implants had no significant influence on strain levels in bone, irrespective of the connection types. Compared with the external hex connection, the Morse-taper connection type presented significantly lower EQV stress values in abutment screws, but significantly higher stress in the bar retaining screw. Increasing the number of implants significantly reduced the EQV stress in the abutment screw and bar retaining screw. Conclusion: The Morse-taper connection type significantly decreased the strain levels in peri-implant bone, while increasing the stress in bar retaining screws. A smaller number of implants in an inferior full-arch rehabilitation slightly increased the stress in the abutment and bar retaining screws. Balanced adjustments of the loading improve the biomechanics of a mandibular full-arch rehabilitation.

Objectives To evaluate clinical, radiographic, microbiologic, and biomechanical parameters related to bone remodeling around implants with external hexagon (EH) and Morse-taper (MT) connections. Materials and Methods Twelve totally edentulous patients received four custom-made implants in the interforaminal region of the mandible. Two of those implants had the same macroscopic design, but different prosthetic connections. All patients received an immediate implant-supported prosthesis. Clinical parameters (periimplant probing pocket depth (PPD), modified gingival index (mGI), and mucosal thickness (MTh)) were evaluated at 12 months follow-up. The distance between the top of the implant and the first bone-to-implant contact (IT-FBIC) was evaluated on standardized digital peri-apical radiographs acquired at 1, 3, 6, and 12 months follow-up. Samples of the subgingival microbiota were collected 1, 3, and 6 months after implant loading and used for the quantification of Tanerella forsythia, Porphyromonas gingivalis, Aggragatibacter actinomycetemcomitans, Prevotella intermedia, and Fusobacterium nucleatum. Further, 36 computerized-tomography based finite element (FE) models were accomplished, simulating each patient under three loading conditions. Results The evaluated clinical parameters were equal for EH and MT implants. Mean IT-FBIC was significantly different between the tested connections (1.17 ± 0.44 mm for EH, and 0.17 ± 0.54 mm for MT, considering all evaluated time periods). No significant microbiological differences could be observed between tested connections. FE analysis showed a significantly higher peak of equivalent (EQV) strain (p = 0.005) for EH (mean 3,438.65 µe) compared to MT (mean 840.98 µe) connection. Conclusions Radiographic periimplant bone loss depends on the implant connection type. MT connections showed less periimplant bone loss, compared to EH connections.

European Association of Osseointegration, EAO 22nd Annual Scientific Meeting, Dublin, Ireland 17-19 October 2013

To evaluate clinical, radiographic, microbiologic, and biomechanical parameters related to bone remodeling around implants with external hexagon (EH) and Morse-taper (MT) connections.Twelve totally edentulous patients received four custom-made implants in the interforaminal region of the mandible. Two of those implants had the same macroscopic design, but different prosthetic connections. All patients received an immediate implant-supported prosthesis. Clinical parameters (periimplant probing pocket depth (PPD), modified gingival index (mGI), and mucosal thickness (MTh)) were evaluated at 12 months follow-up. The distance between the top of the implant and the first bone-to-implant contact (IT-FBIC) was evaluated on standardized digital peri-apical radiographs acquired at 1, 3, 6, and 12 months follow-up. Samples of the subgingival microbiota were collected 1, 3, and 6 months after implant loading and used for the quantification of Tanerella forsythia, Porphyromonas gingivalis, Aggragatibacter actinomycetemcomitans, Prevotella intermedia, and Fusobacterium nucleatum. Further, 36 computerized-tomography based finite element (FE) models were accomplished, simulating each patient under three loading conditions.The evaluated clinical parameters were equal for EH and MT implants. Mean IT-FBIC was significantly different between the tested connections (1.17 ± 0.44 mm for EH, and 0.17 ± 0.54 mm for MT, considering all evaluated time periods). No significant microbiological differences could be observed between tested connections. FE analysis showed a significantly higher peak of equivalent (EQV) strain (p = 0.005) for EH (mean 3,438.65 µε) compared to MT (mean 840.98 µε) connection.Radiographic periimplant bone loss depends on the implant connection type. MT connections showed less periimplant bone loss, compared to EH connections.

It is not yet well understood to what extent different implant-abutment mismatch sizes and implant-abutment connection types may influence the peri-implant biomechanical environment of implants in different clinical situations.Computed tomography-based finite element models comprising a maxillary central incisor socket and 4.5 × 13 mm outer-diameter implants with external and internal hex connection types were constructed. The abutments were designed with diameters of 3.5 mm (platform switching [PS] with 1 mm of diametral mismatch [PS - 1]), 4.0 mm (PS with 0.5 mm of diametral mismatch [PS - 0.5]), and 4.5 mm (conventional matching implant-abutment design [CD]). Analysis of variance at the 95% confidence interval was used to evaluate peak equivalent strain (EQV strain) in the bone, bone volume affected by a strain4,000 με (EQV strain4,000 με), the peak von Mises stress (EQV stress) in abutment screw, and the bone-implant relative displacement.Similar bone strain levels (EQV strain and EQV strain4,000 με) were encountered in PS - 1, PS - 0.5, and CD models for immediately placed implants, independent of the connection type. For immediately loaded implants, slightly smaller peak EQV strain and EQV strain4,000 με were found for PS - 1. However, for both connection types in osseointegrated models, the higher the mismatch size, the lesser the amount of strain found.The increase in mismatch size of PS configuration results in a significant decrease of strain levels in bone for osseointegrated implants, principally for external hex connections. No significant effect of PS could be noted in immediately placed implants.